1. Technical Field
The present invention relates to an optical device, an optical scanner, and an image display apparatus.
2. Related Art
For example, an optical scanner that two-dimensionally scans light is known as an optical device used in a projector or the like (see, for example, JP-A-2009-75587 (Patent Literature 1)).
The optical scanner disclosed in Patent Literature 1 includes a frame, an outer driving section suspended on the frame via a first torsional spring and capable of turning about a first axis, an inner driving section suspended on the outer driving section via a second torsional spring and capable of turning about a second axis orthogonal to the first axis, and a stage arranged on an upper part of the inner driving section and configured to turn together with the inner driving section.
In the optical scanner disclosed in Patent Literature 1, the outer driving section is turned about the first axis and the inner driving section is turned about the second axis by a Lorentz force generated by an electric current flowing to a coil provided in each of the inner driving section and the outer driving section and a magnetic field between a pair of magnets arranged on both sides of the frame.
The stage is coupled to the inner driving section through a link section projecting from the center of a lower part of the stage. The center of gravity of the stage is located on the second axis in plan view. Therefore, inertial moments about the second axis in portions on one side and on the other side of the stage with respect to the second axis are equal.
In this way, in the optical scanner disclosed in Patent Literature 1, it is difficult to excite the inner driving section about the second axis. Therefore, a build-up time is long. The build-up time means time in which a light reflection plate changes from a stop state to a desired swinging state.